1. Field of the Invention
The present invention relates to an image forming apparatus employing an electronic photographic system such as a laser printer, an electronic photographic copier and the like, and a method for notifying toner near-empty.
2. Related Art Statement
In an image forming apparatus 51 employing an electronic photographic system such as a laser printer, an electronic photographic copier and the like, as shown in FIG. 1, first, the photosensitive drum 52 surface is charged to a fixed surface potential by a charge device 53, and subsequently, the photosensitive drum 52 surface is exposed by an exposure device 54 such as a semiconductor laser to attenuate the surface potential to form an electrostatic latent image. And a bias voltage is applied to a developer roller 56 surface of a developer device 55, a toner charged within the developer device 55 is adhered to an electrostatic latent image forming portion of the photosensitive drum 52 surface, the electrostatic latent image forming portion is developed and actualized to form a toner image on the photosensitive drum 52 surface.
On the other hand, a sheet of paper P is caffied to a transfer region by carrier rollers 57, the sheet P is charged by a transfer device 58, and the toner image formed on the photosensitive drum 52 surface is transfeffed to the sheet. Subsequently, the sheet P is peeled off from the photosensitive drum 52 surface by a peel-off device 59, and the toner image is fixed to the sheet P surface by a fixing device (not shown), after which the sheet P is drawn off outside the apparatus by draw-off rollers (not shown).
After the toner image has been transferred to the sheet P surface, the toner remained on the photosensitive drum 52 surface is scraped away and withdrawn by a blade 61 of a cleaning device 60, and subsequently, electric charge remained on the photosensitive drum 52 surface is removed by an electric remover 62 to place the photosensitive drum 52 surface in an initial state.
For example, in the developer device 55 employing a 2-component developing system, a developer D comprising a caffier C as magnetic powder and a toner T as colored resin powder is housed in the developing device, and the caffier C and the toner T are mixed and stirred by stirring screws 63 and 64 so as to charge toner by friction. Where toner T is consumed by development, toner T is supplied into the developing device 55 from a toner cartridge (not shown) disposed upward, and similarly to the above, the supplied toner T and the carrier C are mixed, stirred and charged.
Normally, a toner remaining amount sensor is disposed within the toner cartridge so that the toner remaining amount within the toner cartridge is detected continuously, and where the toner remaining amount is less than a fixed value, a toner near-empty is notified. Further, without providing the toner remaining amount sensor, where image signals forming dots of a print image are counted and the total value thereof is over a fixed value, a toner near-empty is notified.
However, in any of image forming apparatus described above, the toner consumption amount is varied greatly due to the actual using environment such as temperature and humidity of using places, a print image pattern, a sheet consumption amount per hour, and the like, and therefore, there is a problem that the toner near-empty cannot be notified accurately.
For overcoming the above-described problem, there is proposed an image forming apparatus wherein a dot number addition value of a print image in a toner cartridge prior to exchange is amended into a toner near-empty prediction value in a toner cartridge after exchange, and when a dot number addition value of a print image in a toner cartridge after exchange reaches a toner near-empty prediction value, a toner near-empty is notified (Japanese Patent Laid-Open No. 239729/2001 Publication).
However, toner housed in a toner cartridge is normally not consumed in a short period such as two or three weeks, but consumed over a long period such as two or three weeks or more, and therefore, the using circumstances in the toner cartridge prior to exchange and the toner cartridge after exchange are sometimes changed remarkably. Therefore, there is a problem that even if a dot number addition value in a toner cartridge prior to exchange is amended, accuracy is low by only such an amendment for use as a toner near-empty prediction value in a toner cartridge after exchange.
Further, the using frequency of the image forming apparatus greatly changes depending upon month, week, day of the week, time zone of day, and the like, and the toner consumption amount per hour greatly varies accordingly. Furthermore, time required till a toner cartridge is actually exchanged after toner near-empty has been notified is greatly different between where a service man exchanges it and where a user or a manager exchanges it. However, in the above-described image forming apparatus, nothing has been taken into consideration for such a point.